1. Field of the Invention
The invention relates to a receptacle connector including a central terminal mechanically and electrically connecting with a core wire of a coaxial cable connected to a plug connector, and an outer terminal mechanically and electrically connecting with an external conductor surrounding the core wire with an internal electrical-insulator being sandwiched therebetween.
The invention relates further to a terminal used for the receptacle connector.
2. Description of the Related Art
As one of connectors used for connecting a coaxial cable to a printed circuit board, there is known a receptacle connector into which a plug connector connected to a coaxial cable is fit. A receptacle connector is used for transmission of video-camera signals, and transmission of signals for connecting an antenna used for radio-signal communication such as to a printed circuit board, for instance. A coaxial cable having a diameter of about 0.5 mm is connected to a receptacle connector. Various receptacle connectors have been suggested as follows.
FIGS. 13A and 13B illustrate a receptacle connector suggested in Japanese Utility Model Publication No. H7 (1995)-24791.
The illustrated receptacle connector 1000 includes a central terminal 1001, and an external terminal 1002 located around the central terminal 1001 in electrically insulating condition with the central terminal 1001.
The central terminal 1001 stands at a distal end 1004 of a plate-shaped connector 1003. The external terminal 1002 not entirely, but partially surrounds the central terminal 1001. The connector 1003 includes a strip 1005 having a first portion 1005A located closer to the distal end 1004, and a second portion 1005B located away from the distal end 1004. The first portion 1005A is smaller in width than the second portion 1005B. The strip 1005 is connected at the second portion B to a strip line 1007 formed on a surface of a circuit board 1006. As illustrated in FIG. 13A, the strip 1005 is bent at a boundary between the first and second portions 1005A and 1005B such that the first portion 1005A is set higher than the second portion 1005B, and further, as illustrated in FIG. 13B, the first portion 1005A is smaller in width than the second portion 1005B. This is because a height from a lower surface of the circuit board 1006 to the first portion 1005A and a height from a lower surface of the circuit board 1006 to the second portion 1005B are different from each other, and accordingly, an effective dielectric constant below the first portion 1005A and an effective dielectric constant below the second portion 1005B are different from each other. Even if an effective dielectric constant varies in dependence on an area of the strip 1005, an impedance characteristic can be adjusted between the first and second portions 1005A and 1005B by partially varying a width of the strip 1005. As shown in FIG. 13A, a plug connector 1010 has a plug conductor 1011 which makes contact with the central terminal 1001 of the receptacle connector 1000 and a coaxial cable 1012 whose core conductor 1013 is connected to the plug conductor.
FIG. 14 illustrates a receptacle connector suggested in Japanese Patent Application Publication No. 2010-272244.
The illustrated receptacle connector 1100 includes a housing 1101 made from an electrically insulating plate and having a substantially rectangular cross-section, a central terminal 1102, and an external terminal 1103. The central terminal 1102 and the external terminal 1103 are fixed to the housing 1101 by insert molding such that they are coaxial with each other. The central terminal 1102 is solid, and the external terminal 1103 is in the form of a cylinder such that the central terminal 1102 is located at a center of the external terminal 1103. Contact supports 1104 and 1105 extend almost horizontally in the housing 1101 along a lower surface of the housing 1101. The contact supports 1104 and 1105 have lower surfaces extending on a level with a lower surface of the housing 1101, and exposed downwardly.
In the receptacle connector 1000 illustrated in FIGS. 12A and 13B, the external terminal 1002 is designed to partially surround the central terminal 1001 therewith. In the receptacle connector 1100 illustrated in FIG. 14, the external terminal 1103 is designed to be cylindrical. For instance, the external terminal in the receptacle connector 1000 illustrated in FIGS. 13A and 13B were designed to be annular, the connector 1003 has to be designed to extend below the external terminal 1002.
If the connector 1003 extends below the external terminal 1002, even if an impedance were adjusted between the first and second portions 1005A and 1005B, a capacitance to be generated between the external terminal 1002 and the central terminal 1001 would exert harmful influence on the impedance adjustment.
An electric connector used for connecting a coaxial cable with a printed circuit board is recently required to be smaller and smaller in size, and hence, a distance between the external terminal 1002 and the central terminal 1001 is smaller and smaller. Thus, the impedance adjustment becomes more and more difficult.